Hi 'Boston brad,'
It all "depends."
You did not say in what tests with what kind of BGS and what kind of details
4000 vs 4500 cycles were gotten for SMD vs NSMD. It makes a big difference.
For relatively behign T-cycles the difference is about 30%, whereas for
severe T-cycles I have seen a factor of 3 differences. This is for OMPAC-type
BGAs; for Tessera-design CSPs the difference will be much smaller. Whether
both, NSMD, or neither is reliable for a given application depends on the
details. For "How far in the reliability range does one have to be???," you
may want to take a look at Appendix A of IPC-9701.

Werner Engelmaier

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